From the founding of Mitsui Memorial Hospital to the 1900s-1930s

	October 1906 Mitsui Hachirouemon, representing the Mitsui family, establishes the Mitsui Charity Hospital as an incorporated foundation March 1909 The Hospital is formally opened on the site of the former Tokyo Imperial University Second Hospital in Kanda-Izumicho, Chiyoda-ku, Tokyo April 1919 The name is changed to Izumibashi Charity Hospital

1940s and 1960s

July 1943 The name is changed to Mitsui Public Welfare Hospital March 1945 The buildings and attached facilities are destroyed by fire bombs August 1947 Major repairs are completed on two 3-story reinforced concrete buildings April 1951 Expansion of wards by 500 sq.m., with 50 new beds May 1952 The name is changed to Mitsui Welfare Hospital, a social welfare corporation November 1956 Expansion of wards by 780 sq. m., with 58 new beds

1970s and 1980s

	April 1970 The name is changed to Mitsui Memorial Hospital, a social welfare corporation The old buildings are dismantled, and the first stage of construction of the present buildings is completed (Ward Blocks B and C) April 1980 The second stage of construction is completed (Ward Block D) April 1983 The third stage of construction is completed (Nursing School, Nurses' Residence)

From the 1990s to the 2000s

	August 1993 The Administration Building is completed August 1994 The Comprehensive Examination Center is completed May 2002 Mitsui Yokoen Special Nursing Home for the Elderly March 2004 The Mitsui Memorial Hospital Nursing School is opened in Koto-ku December 2008 Opening of the Inpatient Wards September 2010 Opening of the Outpatient Ward Block